Different types of wireless communication systems have been developed to provide different types of services. Some examples of the wireless communication systems include wireless local area network (WLAN), wireless wide area network (WWAN) and cellular networks such as universal mobile telecommunication systems (UMTS). Each of these systems have been developed and tailored to provide specific applications.
With the pervasive adoption of wireless communication networks in enterprise, residential and public domains, continuous connectivity can be supported as the users of such networks move from one network to the other. With the emerging “always-on” life style, wireless transmit/receive units (WTRUs), (i.e., mobile stations (MS)), are required to support multiple heterogeneous networks. Thus, a seamless handover between these networks is desired.